Diesel fuel



Patented Dec'. 7, 19 43 DIESEL FUEL John H. McCracken and Edwin M. Nygaard, Woodbury, N. J., assignors to Socony-Vacuum Oil Company, Incorporated, a corporation of New York No Drawing. Application May 2, 1942 Serial'No. 441,536

(CI. 44-57) products, perchloromethylmercaptan is reacted 7 Claims.

This invention relates to fuels for internal combustion engines of the Diesel or compression ignition type, and more particularly relatesto the improvement of such non-viscous hydrocarbon fuels by the addition thereto of a characterizing agent.

In Diesel engine operation, a liquid fuel is injected into a combustion. chamber and ignited by compression. In order that maximum efficiency be attained, the delay period between the inart, numerous compounds have been proposed "for use in Diesel fuels to improve the ignition quality of said fuels. Small amounts of such compounds incorporated in the fuel act as ignition accelerators. By such means, the better grades of Diesel fuels are improved, and the low grade fuels are improved so as to have greater value.

The present invention is predicated upon the discovery that Diesel fuels of improved ignition quality can be obtair. l by admixing with the fuel a minor proportion of a reaction product of perchloromethylmercaptan (ClsCSCl) and disubstituted dithiophosphoric acid.-

Perchloromethylmercaptan, as indicated by the formula above, is a chlorine substituted sulfur chloride and can be prepared by the chlorination of carbon disulfide according to the' method of Helfrich and Reid (J. Amer. Chem. Soc. 43, 591 (1921)). Forexample carbon disulfide containing about 0.4% byweight of iodine was chlorinated in 'the absence of direct sunlight at a temperature maintained below C.

until the volume of the reaction mixture had' doubled. The crude product, which has been topped to remove carbon tetrachloride and sulfur dichloride contains perchloromethylmercaptan, with some sulfur monochloride. This "crude product can be used in the preparation of the reaction products contemplated herein, although in the exai iples cited herein a fractionated product was used.

In order to obtain our new and novel reaction with'a disubstituted dithiophosphoric acid represented by the formula RO s I RO/ sn wherein R is alkyl or aralkyl. As contemplated herein, the dithiophosphoric acid may be substituted with two alkyl groups, two aralkyl groups, or an alkyl group and an aralkyl group. Di-substituted dithiophosphoric acids useful for the purposes of this invention may be prepared by any of the several methods of preparation known to the art, as for example, those described in the following publications: P. S. Pishchmuka, J. Russ. Phys. Chem. Soc. 56, 11 (1925) (C. A. 19, 2808 (1925) P. -s. Pishchmuka,- J. Chim. Ukraine 1, 87 (1926) (C. A. 20, 2816 (1926)); Kovalevsky, Ann. 119, 303 (1861) contemplated also as a preferred reactant with perchloromethylmercaptan is a reaction product, predominantly comprised of adisubstituted dithiophosphoric acid, obtained by the reaction of an alcohol-specifically R.OH in which R is alkyl or aralkyl-and P285. Particularly preferred is that reaction product obtained by the reaction of four mols of said'alcohol and one mol of P285. It will be seen, there can be served by the use of a reaction product of perchloromethylmercaptan' and either a pure disubstituted dithiophosphoric acid, as given by the formula above, or a crude reaction product predominantly comprised of a disubstituted dithiophosphoric acid,

Typical alcohols represented by the formula R.0H in which R is alkyl or aralkyl are the followihgi'methyl, ethyl,- propyl, butyl', octyl (2- fun, that the purposes of the present invention of the present invention are methyl and butyl alcohols.

Although the mechanism of the reaction of perchloromethylmercaptan and a disubstituted idithiophosphoric acid is not yet thoroughly understood, it'is probable that the reaction proceeds in the following manner:

wherein R is either alkyl or aralkyl. However, we do not wish to be bound by the theory of reformula action set forth above and the present invention is therefore not limited to compounds of the (A) i 'repamu'on of dibutyl dithiophosphoric acid Into a three-neck flask of suitable size, fitted with stirrer, reflux condenser and thermometer, were placed 1 part of P2S5,-1.2'l parts of n-butyl alcohol and 1 part of carbon dlsulfide. The reaction was allowed to proceed at 30 C. for 1.5 hours and at 50 C. for the next-2 hours. The

. product was filtered and the solvent, along with any excess alcohol," was removed by toppingv at 90 C. with the aid of laboratory vacuum (about 200 mine). The product was a yellow oil having a peculiar green cast. The theoretical neutraliza tion number (N. N.) for dibutyl-dithiophosphoric acid is 232; the neutralization number found for the product was 218. i

(B) Into a three neck flask, fitted with stirrer, reflux condenser and dropping funnel, were placed 1.3 parts of dibutyl dithiophosphoric acid (prepared in A) and about 3 parts of low-boiling ample one-A, a reaction product predominantly comprised of dimethyl dithiophosphoric acid was prepared from 1 part methanol and 1.74 parts petroleum ether. During one -hour,'a solution of 1 part of perchloromethylmefcaptan dissolved in about 3 parts of petroleum ether wasslowly added. That the reaction proceeded smoothly was indicated by copious evolution of hydrogen chloride throughout the addition of perchloromethylmercaptan. When the addition was flnished the mixture was stirred for 0.5 hour to complete with distilled water and then dried over sodium sulfate. 7 The solvent was removed by distillation mercaptan. The product contained 23.l per cent sulfur and 22.2 per cent chlorine.

As aforesaid; crude reaction products of an alcohol and P285 in which the predominant product is a disubstituted. dithinpliosphorie acid may. be reacted with perchloromethylmercaptan to o of PzSs with about 2 parts of carbon disulflde as the solvent. Calculated for dimethyl dithiophosphoric acid: N; N. 354: S, 40.5 per cent;.found: N. N.,- 220: S, 28.1 per cent.

(B) The procedure in Example one (B) was followed in preparing the reaction product of perchloromethylmercaptan and crude dimethyl .dithiophosphoric acid; As the acid was not miscible with petroleum ether, 1 part of the acid was added to a solution of 1.17 parts Of perchloromethylmercaptan dissolved in about 3 parts of petroleum ether. The product contained 34 per cent sulfur and 21.4 per-cent chlorine.

The effectiveness of the reaction products of perchloromethylmercaptan and disubstituted dithiophosphoric acids eontemplatedherein in improvidlng the ignition qualities of Diesel fuels is demonstrated by comparatve results of a fuel blank and fuel blends. The ignition quality of the fuel and th fuel blends was determined by comparison with a standard reference fuel in a. converted C. F. R. engine using the ignition delay method. The value obtained in this test is expressed as the cetane number which is the per cent by volume of cetane and alphamethyl naphthalenev having the same combustion characteristics as the sample under test. (Reference:

Proc. Am. Soc. Testing Materials, vol. 38.1, 392; (1938).) The effectiveness of the new and novel reac- 5 tion products contemplated herein is further demonstrated by comparison of fuel oil blends voi! typical reaction products with such blends of typical individual reactants, as for example, perchloromethylmercaptan, dibutyl dithiophosphoric acid and crude dimethyl dithiophosphoric acid. Perchloromethylmercaptan has previously been proposed as a Diesel fuel improving agent; however, as shown by the following data given in Table 1, this compound isinuch less effective the reaction.v The petroleum ether solution was washed with sodiumbicarbonate solut on,

tain react on p oducts w ich maybe used for the purposes of this invent on.' .Exarnple two given below descr be the p eparat n. and properties. of a typical product .which. as later demonstrated herein, is an effective Diesel fuel improvins agent.

Using the same procedure as described in Ex- Gravity, "A. P. 1 28.8 Flash point (Pensky-Martens) 200 Aniline point, F 122 A. S. T. M. distillation. F:

Initial 431 10% 46'! 90% 582 End point 629 Diesel index 7 35.1 Cetane number 33.0

Table 1 i V Y Per cent Cetane Increasein Substance blended with mu by wt. number of octane added blend number Perchlo'romethylmerca t'an 1.0 33.9 0.0 Crude dimethyl dit iophoshorlc acid 1.0 35.5 2.5 D butyl dithiophosnhoric acld. 1.0 35.0 2.0 Reaction product of perchloramethyhnercaptm and crude dimethyl dithiophosphoric acid 1.0. 39.0 0.0 Reaction product of perchloramothylmereepten and 'dibutyl dithlop osphotic ncid 1.0 1 40.0 7.0

than the reaction products contemplated herein. The Diesel fuel oil used is a catalytically cracked number 2 fuel oil having the following characteristics.

It will. be readily observed from the foregoing results that the reaction products of pertained by the reaction of perchlorometiiylmerchloromethylmercaptan and dlsubstituteddithiophosphoric acids contemplated herein are I effective to improve the ignition quality of a typical Diesel fuel, and are far superior in this 1 regard to the individual reactants-perchloromethylmercaptan and typical disubstituted dithiophosphoric acids.

The term Diesel fuel, as used herein has reference to those non-viscous petroleum fractions, commonly denoted in the art as Diesel fuels, and to those hydrocarbon oils in general whose physical characteristics render them suitable for use as fuels in compression ignition engines.

The reaction products contemplated herein may be used in amounts ranging from 0.1 per cent to about 5.0 per cent, and it is to be understood that while we. have herein described preferred proceduresfor preparing the same, the invention is not confined to products made by such procedure; but includes within its scope whatever charge or departures fairly come within the spirit of the appended claims.

We claim:

1. An improved Diesel fuel comprising a hydrocarbon fuel oil and in admixture therewith a minor proportion of a reaction product obtained by, the reaction of perchloromethylmercaptan with a compound selected from the group consist- -ing of a dialkyl dithiophosphoric acid, a diaralkyl-dithiophosphoric acid and an alkyl-aralkyl-dithiophosphoric acid, said compound being represented by the formula R--0\- s P/ R-O sn wherein R is selected from the group consisting of alkyl and aralkyl groups.

2. An improved Diesel fuel comprising a hydrocarbon fuel oil and in admixture therewith a minor proportion of the reaction product obtained by the reaction of perchloromethylmercaptan with dibutyl dithiophosphoric acid, said acid being represented by the formula 3. An improved Diesel fuel comprising a hydrocarbon fuel oil and in admixture therewith a minor proportion of the reaction product ob tained by the reaction of perchloromethylmer- I captan with dimethyl dithiophosphoric acid,

Inc-o s y mc-o \SH 4. An improved Diesel fuel comprising a hydrocarbon fuel oil and in admixture therewith a minor proportion of the reaction product chcaptan with the reaction product obtained by reaction of one mol of P285 and four mols of an alcohol, the latter reaction product being predominantly comprised of a disubstituted dithiophosphoric acid represented by the formula 6. .An improved Diesel fuel comprising a nonviscous petroleum oil and in admixture therewith a minor proportion, suflicient to decrease the ignition delay period of the fuel, of a reaction product obtained by the reaction of perchloromethylmercaptan with a compound selected from the group consisting of a dialkylr-dithiophosphoric acid, a diaralkyl-dithiophosphoric acid and an alkyl-aralkyl-dithiophosphoric acid, said compound being represented by the formula RO\ /s wherein R is selected from the group conslstmg of alkyl and aralkyl groups.

'1. An improved Diesel fuel comprising a nonviscous petroleum oil and in admixture therewith a minor proportion, from about 0.1 per cent to about 5.0 per cent, of a reaction product obtained by the reaction of perchloromethylmercaptan with a compound selected from the group con sisting of adialkyl-dithiophosphoric acid, a diaralkyl-dithiophosphoric acid and an alkyl-aralkyl-dithiophosphoric acid, said compound being represented by the formula 3-0 \H wherein R is selected from the group consisting of alkyl and aralkyl groups.

JOHN H. McCRAC KEN. EDWIN M. NYGAARD. 

